Contrary to popular belief, one paintball gun is not made to shoot harder than another. All paintball fields have a regulation fps (feet per second) that they allow their customers to shoot their guns at. If the velocities are all around the same, then all the guns there will shoot about the same distance, and none of them will shoot farther or "harder."
There are many reasons as to why you actually do not want your gun to shoot too fast. Besides the obvious safety factor, Paintball fields have a regulation speed, generally a max of 280-300 FPS. Shooting any faster than that can cause issues while shooting such as chopping paint, inaccuracy, and internal issues with your marker.
If distance is specifically what you’re looking for, there are some set ups that help you slightly. Tippmann’s Flatline System and Tiberius Arms’ First Strike paintball rounds (only to be used in paintball markers specified for First Strike) are products known to give you a bit more distance without tampering with the marker’s velocity.